Apparatus for cooling liquids

ABSTRACT

The cooling apparatus is especially advantageous for cooling hot viscous liquids such as hot phosphoric acid. The liquid is contained in a generally cylindrical tank having an axial down draft tube with a pumping propeller therein. The liquid passes over a circular weir at the upper end of the tube and is pumped downwardly by the propeller. At the lower end of the tube, the liquid is deflected outwardly in all radial directions by a generally conical deflector. The liquid is then deflected upwardly by a frustoconical or parabolic deflector. A large number of cooling coils or plates are positioned in radial longitudinal planes in the tank so that the liquid passes upwardly through the spaces between the coils. Cooling water or the like is circulated through the coils between ring-shaped header pipes disposed above the coils. A cylindrical baffle projects downwardly between the weir and the cooling coils so that the liquid must pass under the baffle to get to the weir. The shaft for the propeller passes downwardly through a tube having longitudinal radial vanes which suppress whirling of the liquid above the propeller.

United States Patent [72] Inventor Lewis H. Durdin P.O. Box 1148, Birmingham, Ala. 35201 [21] Appl. No. 846,748 [22] Filed Aug. 1. 1969 [45] Patented July 27, 1971 [54] APPARATUS FOR COOLING LIQUIDS Primary Examiner- Frederick L. Matteson Assistant Examiner-Theophil W. Streule Atlorney- Burmeister. Palmatier and Ham by ABSTRACT: The cooling apparatus is especially advantageous for cooling hot viscous liquids such as hot phosphoric acid. The liquid is contained in a generally cylindrical tank having an axial down draft tube with a pumping propeller therein The liquid passes over a circular weir at the upper end of the tube and is pumped downwardly by the propeller. At the lower end of the tube, the liquid is deflected outwardly in all radial directions by a generally conical deflector. The liquid is then deflected upwardly by a frustoconical or parabolic deflector. A large number of cooling coils or plates are positioned in radial longitudinal planes in the tank so that the liquid passes upwardly through the spaces between the coils. Cooling water or the like is circulated through the coils between ring-shaped header pipes disposed above the coils. A cylindrical baffle projects downwardly between the weir and the cooling coils so that the liquid must pass under the baffle to get to the weir. The shaft for the propeller passes downwardly through a tube having longitudinal radial vanes which suppress whirling of the liquid above the propeller.

M04110. LEVEL 52 PATENTED JUL27 l9?! SHEET 2 BF 2 FIG, 2

I V (I I. l

APPARATUS FOR COOLING LIQUIDS This invention relates to an apparatus for cooling liquids, particularly extremely hot liquids'which are highly viscous. The cooling apparatus is especially advantageous for cooling hot superphosphoric acid. Such apparatus is needed in plants for manufacturing superphosphoric acid, which is generally produced by burning elemental phosphorous, and then hydrating the resultant gaseous oxide. The superphosphoric acid produced by this process is extremely hot, typically about 350 F. Moreover, the viscosity of the acid is often very high, ranging up to about 230 centipoises, for extremely concentrated acid having the equivalent of H percent of H 1 0, Typically, it is desirable to cool the superphosphoric acid to about 250 F. so that it can be handled safely and conveniently.

Difficulties have been experienced with prior cooling devices, because of the extremely hot, viscous and corrosive character of the super phosphoric acid. It has been difficult to bring about a sufficient heat exchange between the hot acid and the usual cooling coils or plates to achieve efficient cooling. Prior cooling equipment has been troublesome and short lived. The impact of the hot acid on various components of prior cooling devices has had an erosive as well as a corrosive effect, so that critical components have been quickly destroyed or damaged.

One object of the present invention is to provide a cooling device which causes the hot acid or other liquid to flow in an efficient manner along a large number of cooling coils or plates so that efficient cooling is achieved. The flow of the hot acid is controlled in such a manner that the components ofthe cooling device are not overstressed or eroded.

In general, the present invention comprises a generally cylindrical tank for holding the hot acid or other liquid to be cooled. A downdraft tube is disposed axially in the tank. A propeller is located in the tube and is continuously rotated so as to pump the liquid downwardly through the tube. Theliquid discharged from the lower end of the tube is deflected outwardly in all radial directions by a generally conical deflector. The liquid is then deflected upwardly by an annular deflector which flares outwardly and upwardly. A large number of cooling coils or plates are disposed in the tank above the annular deflector so that the liquid is caused to flow upwardly between the coils. The cooling coils or plates are disposed in generally radial planes so that the hot liquid flows along both sides of each plate. The liquid flows into the upper end of the downdraft tube and is recirculated by the propeller. Preferably, the upper end of the downdraft tube is flared to produce a circular weir which controls the flow of the liquid into the tube. A cylindrical baffle is preferably provided between the weir and the upper portions of the cooling coils, so that the liquid must pass under the baffle to reach the weir. The drive shaft for the propeller preferably extends downwardly into the downdraft tube through a supporting tube having longitudinal radial vanes to suppress whirling of the liquid above the propeller.

Further objects, advantages and features of the present invention will appear from the following description, taken with the accompanying drawings, in which:

FIG. 1 is a vertical section taken through a cooling device or apparatus to be described as an illustrative embodiment of the present invention.

FIG. 2 is a horizontal section taken generally along the line 2-2 in FIG. 1.

FIG. 3 is another horizontal section, taken the line 3-3 in FIG. 1.

FIG. 4 is a fragmentary vertical section showing a modified construction for the lower portion of the cooling device.

It will be seen that FIGS. 1-3 illustrate a cooling apparatus or device which will find many uses, but is especially applicable to the cooling of hot superphosphoric acid, or various other hot viscous liquids. The illustrated cooling apparatus 10 comprises an upright generally cylindrical tank 12, adapted to generally along 2 hold a considerable quantity of the liquid to be cooled. The tank 12 is completely closed, in that it has a bottom wall 14, a cylindrical sidewall 16, and a top wall or cover 18. The sidewall 16 is reinforced by an external frame 20. In this case, a cylindrical safety shield 22 is mounted on the frame and is spaced outwardly from the cylindrical sidewall 16, to prevent any person from coming into contact with the sidewall 16, which may become very hot, inasmuch as the superphosphoric acid enters the tank 12 at a high temperature, typically about 350 F. As shown, the bottom 14 of the tank 12 is supported at a pit level 24 which is substantially below the working floor level 26.

Means are provided to admit the hot liquid to the tank 12 and to draw off the cooled liquid. In this case, two inlets 28 and 30 are provided, in the form of pipe stubs connected to the sidewall 16 and projecting outwardly therefrom. It will be understood that inlet pipes may be connected to the inlet stubs 28 and 30. As shown, the inlet stubs 28 and 30 are'located on the upper portion of the sidewall 16. The tank 12 is also provided with an outlet 32 in the form ofa stub to which an outlet pipe may be connected. The outlet stub 32 extends through the sidewall 16 near the bottom wall 14.

Within the tank 12, provision is made for circulating the hot superphosphoric acid or other liquid to be cooled. Thus, the illustrated tank 12 is provided with an axial downdraft tube 34, through which the hot liquid is circulated downwardly. Pumping means are provided to bring about such circulation. In the illustrated cooling device 10, such pumping means include a propeller 36 which is located within the downdraft tube 34. The illustrated propeller36 is mounted on the lower end of a rotatable drive shaft 38 which is journaled within a stationary supporting tube 40. It will be seen that the supporting tube 40 is secured to the cover 18 of the tank 12 and extends downwardly into the upper portion of the downdraft tube 34. The propeller shaft 38 is driven by a motor 42 preferably of the variable speed type, mounted on the upper side of the cover 18.

The supporting tube 40 is preferably provided with a plurality of longitudinal radial vanes 44 which straighten the flow of the liquid into the downdraft tube 34 and prevent or suppresswhirling movement of the liquid above the propeller 36. Four such vanes are provided in the illustrated construction.

The illustrated downdraft tube 34 has a cylindrical portion 46, within which the propeller 36 is located. The cylindrical portion 46 is the smallest portion of the downdraft tube 34 and thus may be characterized as the throat of the tube.

Above the throat portion 46, the downdraft tube 34 has a generally frustoconical portion 48 which flares upwardly and outwardly, in the manner of a funnel, and is surmounted by a generally cylindrical portion 50. During normal operation, the level of the hot liquid is above the upper edge of the cylindrical portion 50, which thus forms a circular weir, over which the hot liquid flows into the downdraft tube 34.

The minimum, normal and maximum liquid levels are indicated in FIG. 1 at 52, 54 and 56. The minimum liquid level 52, at the lower extremity of the inlet 28, is substantially above the circular weir 50. The normal liquid level 54 is at the upper extremity of the inlet 28, while the maximum liquid level is somewhat higher. The rate at which the hot liquid flows over the circular weir 50 may be varied somewhat by changing the level ofthe liquid in the tank 12.

Below the cylindrical throat portion 46 the downdraft tube 34 has a lower portion 58 which extends downwardly in the tank to a level near the bottom 14 thereof. In this case, the lower portion 58 flares outwardly and downwardly so that it is frustoconical in shape. Thus, the lower end of the lower portion 58 is somewhat larger than the throat 46.

A first deflector 60 is provided in the bottom portion of the tank 12, opposite the lower end of the downdraft tube 34, to deflect the hot liquid outwardly in all radial directions along the bottom 14 of the tank. As shown in FIG. 1, the deflector 60 is substantially conical in shape. The deflector 60 projects upwardly from the bottom wall 14 and projects to some extent into the flaring lower portion 58 of the downdraft tube 34. The hot liquid is deflected outwardly through an annular opening 62 between the tank bottom 14 and the lower end of the downdraft tube 34.

After being deflected outwardly, the hot liquid is deflected upwardly by a second deflector 64, spaced outwardly on the tank bottom 14 from the first deflector 60. The second deflector 64 flares upwardly and outwardly and is generally frustoconical in shape. The outlet stub 32 enters the tank 12 through the second deflector 64.

The second deflector 64 directs the hot liquid upwardly so that it flows along and between a plurality of cooling units 66, mounted in the tank 12 around the downdraft tube 34. The cooling units 66 are in the form of cooling coils or plates, through which cold water or some other coolant is circulated. As shown in FIGS. l3, the cooling units 66 are disposed in longitudinal radial planes, between the downdraft tube 34 and the cylindrical sidewall 16. A large number of the cooling units 66 are spaced at angular intervals around the central downdraft tube 34.

Means are provided to circulate cooling water or some other coolant through the cooling units 66. As shown, the cooling water or other coolant is brought into and out of the tank 12 by inlet and outlet pipes 68 and 70, connected to header pipes 72 and 74 within the tank 12. The illustrated header pipes 72 and 74 are annular in shape and are disposed concentrically above the cooling units 66. Branch pipes 76 and 78 are connected between each cooling unit 66 and the header pipes 72 and 74. The inlet and outlet pipes 68 and 70 extend through the top wall or cover 18 ofthe tank 12.

Each cooling unit 66 provides a sinuous passage or coil 80 for the cooling water, so that there will be heat transfer between the hot liquid and the cooling water.

After passing between the cooling units or plates 66, the hot liquid is recirculated through the downdraft tube 34. However, to provide for a more efficient cooling action, a generally cylindrical baffle 82 is interposed between the circular weir 50 and the upper portions of the cooling units 66. As shown, the cylindrical baffle 82 is secured to the cover 18 and projects downwardly between the weir 50 and the upper portions of the cooling units 66. In order to get to the weir 50, the liquid must pass under the cylindrical baffle 82 and then upwardly between the baffle and the downdraft tube 34.

FIG. 4 illustrates a modified construction in which the conical deflector 60 is replaced with a first deflector 84 which is generally conical in shape, but is curved and sharply pointed. Thus, the deflector 84 flares downwardly and outwardly along a smooth curve. Similarly, the frustoconical second deflector 64 is replaced with a curved deflector 86 which is generally parabolic in shape. The curvature of the second deflector 86 merges smoothly with the curvature of the first deflector 84 so that the hot liquid is deflected outwardly and then upwardly with improved efficiency.

It may be helpful to summarize the operation of the cooling apparatus 10. The tank 12 is filled to the normal level with hot superphosphoric acid, or some other liquid to be cooled. The motor 42 is energized so as to rotate the propeller 36, which causes the hot liquid to flow over the circular weir 50 and into the downdraft tube 34. The liquid is propelled downwardly through the flaring lower portion 58 ofthe downdraft tube and is deflected outwardly in all directions along the bottom 14 of the tank 12 by the conical first deflector 60. The liquid is then deflected upwardly by the frustoconical second deflector 64. The deflectors 60 and 64 are capable of controlling the flow of the hot, highly viscous liquid in an efficient manner.

The hot liquid passes upwardly through the spaces between the longitudinal radial cooling units or plates 66. Cooling water or some other coolant is circulated along the passages or tubes 80 in the cooling units. Thus, there is an efficient exchange of heat between the hot liquid and the cooling units 66. The hot liquid flows between the cooling units 66 in a turbulent manner, but the cooling units do not seriously impede the flow of the highly viscous liquid. The cooling water is brought into and out of the cooling apparatus by the inlet and outlet pipes 68 and 70 and the annular inlet and outlet headers 72 and 74.

In order to be recirculated, the hot liquid passes under the cylindrical baffle 82, and then upwardly within the baffle, before flowing over the circular weir 50. The baffle 82 assists in regulating the flow of liquid over the circular weir.

The hot liquid may be drawn out of the tank 12 through the outlet stub 32. The tank may again be filled with hot liquid through either or both of the inlet stubs 28 and 30.

The cooling apparatus provides efficient circulation of the hot viscous liquid, so that a minimum amount of power is required to circulate the liquid. Moreover, maximum contact and transfer of heat are achieved between the liquid and the cooling units 66. The flow of the hot viscous liquid is not blocked or seriously impeded by the cooling units. Thus, the cooling units are not subjected to any excessive stresses or erosion due to the impact of the hot viscous liquid. The tank and all other components which come into contact with the hot liquid are preferably made of stainless steel or some other material which is highly resistant to corrosion. Thus, the cooling apparatus has a long life of trouble-free service.

Various other modifications, alternative constructions and equivalents may be employed, as will be understood by those skilled in the art.

lclaim:

l. A device for cooling a hot viscous liquid or the like,

comprising the combination of an upright tank for holding the liquid to be cooled,

a downdraft tube disposed centrally in said tank,

a rotary propeller mounted in said tube for pumping the liquid downwardly therein,

a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank,

a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly,

a plurality of cooling units disposed in said tank between the outside of said downdraft tube and the inside of said tank so that the liquid passes upwardly along said cooling units before being recirculated by said propeller,

said downdraft tube comprising an upper entrance portion spaced inwardly from said cooling units,

and a generally cylindrical baffle extending downwardly between said entrance portion and said cooling units whereby the liquid is required to travel under the lower end of said baffle and then upwardly between said baffle and said entrance portion before entering said downdraft tube.

2. A device according to claim 1,

in which said cooling units comprise cooling coils which radiate outwardly relative to said downdraft tube and are disposed in generally longitudinal radial planes.

3. A device according to claim 1,

in which said cooling units radiate outwardly relative to said downdraft tube and are disposed in generally longitudinal radial planes,

said cooling units comprising cooling coils,

first and second annular header pipes for carrying a coolant to and from said coils,

and inlet and outlet pipes connected to said header pipes,

said cooling coils being connected between said first and second header pipes.

4. A device according to claim 1,

including an axial supporting tube extending downwardly into the upper portion of said downdraft tube to support said propeller,

a drive shaft rotatably mounted in said supporting tube and connected to said propeller,

and a plurality of longitudinal vanes projecting outwardly from said supporting tube to suppress whirling movement of the liquid above said propeller.

5. A device for cooling a hot viscous liquid or the like,

comprising the combination of an upright tank for holding the liquid to be cooled,

a downdraft tube disposed centrally in said tank,

substantially cylindrical baffle means encompassing the entrance area about said drum draft tube,

a rotary propeller mounted in said tube for pumping the liquid downwardly therein,

a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank,

a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly,

a plurality of cooling units disposed in said tank between the outside of said downdraft tube and the inside of said tank the liquid to be cooled,

a downdraft tube disposed centrally in said tank,

substantially cylindrical baffle means disposed outwardly of said downdraft tube,

a rotary propeller mounted in said tube for pumping the liquid downwardly therein,

a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank,

a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly,

a plurality of generally flat cooling coils disposed in said tank between the outside of said downdraft tube and the inside of said tank so that the liquid passes upwardly between said cooling coils before being recirculated by said propeller,

said cooling coils radiating outwardly relative to said downdraft tube and being disposed in generally longitudinal-radial planes,

first and second annular header pipes disposed in said tank above said coils for carrying a coolant to and from said coils,

and inlet and outlet pipes connected to said header pipes,

said coils being connected between said header pipes.

Q UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION kaaent No. 3,595, 308 Dated July 27, 1971 l'zrwentofls) LEWIS H. DURDIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[emu

5, line 5, "drum draft" should be corrected to read -downdraft-.

Signed and sealed this 25th day of January 1972.

P'LFLETCHERJR- ERIC-BERT GOTTSCHALK 4; esting officar' c i ioner of Paten 

1. A device for cooling a hot viscous liquid or the like, comprising the combination of an upright tank for holding the liquid to be cooled, a downdraft tube dispOsed centrally in said tank, a rotary propeller mounted in said tube for pumping the liquid downwardly therein, a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank, a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly, a plurality of cooling units disposed in said tank between the outside of said downdraft tube and the inside of said tank so that the liquid passes upwardly along said cooling units before being recirculated by said propeller, said downdraft tube comprising an upper entrance portion spaced inwardly from said cooling units, and a generally cylindrical baffle extending downwardly between said entrance portion and said cooling units whereby the liquid is required to travel under the lower end of said baffle and then upwardly between said baffle and said entrance portion before entering said downdraft tube.
 2. A device according to claim 1, in which said cooling units comprise cooling coils which radiate outwardly relative to said downdraft tube and are disposed in generally longitudinal radial planes.
 3. A device according to claim 1, in which said cooling units radiate outwardly relative to said downdraft tube and are disposed in generally longitudinal radial planes, said cooling units comprising cooling coils, first and second annular header pipes for carrying a coolant to and from said coils, and inlet and outlet pipes connected to said header pipes, said cooling coils being connected between said first and second header pipes.
 4. A device according to claim 1, including an axial supporting tube extending downwardly into the upper portion of said downdraft tube to support said propeller, a drive shaft rotatably mounted in said supporting tube and connected to said propeller, and a plurality of longitudinal vanes projecting outwardly from said supporting tube to suppress whirling movement of the liquid above said propeller.
 5. A device for cooling a hot viscous liquid or the like, comprising the combination of an upright tank for holding the liquid to be cooled, a downdraft tube disposed centrally in said tank, substantially cylindrical baffle means encompassing the entrance area about said drum draft tube, a rotary propeller mounted in said tube for pumping the liquid downwardly therein, a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank, a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly, a plurality of cooling units disposed in said tank between the outside of said downdraft tube and the inside of said tank so that the liquid passes upwardly between said cooling units before being recirculated by said propeller, an axial supporting tube extending downwardly into the upper portion of said downdraft tube to support said propeller, a drive shaft rotatably mounted in said supporting tube and connected to said propeller, and a plurality of longitudinal vanes projecting outwardly from said supporting tube to suppress whirling movement of the liquid above said propeller.
 6. A device for cooling a hot viscous liquid or the like, comprising the combination of an upright tank for holding the liquid to be cooled, a downdraft tube disposed centrally in said tank, substantially cylindrical baffle means disposed outwardly of said downdraft tube, a rotary propeller mounted in said tube for pumping the liquid downwardly therein, a first deflector disposed in said tank below said tube for deflecting the liquid outwardly into the lower portion of said tank, a second deflector spaced outwardly from said first deflector for deflecting the liquid upwardly, a plurality of generally flat cooling coils disposed in said tank between the outside of said downdraft tubE and the inside of said tank so that the liquid passes upwardly between said cooling coils before being recirculated by said propeller, said cooling coils radiating outwardly relative to said downdraft tube and being disposed in generally longitudinal radial planes, first and second annular header pipes disposed in said tank above said coils for carrying a coolant to and from said coils, and inlet and outlet pipes connected to said header pipes, said coils being connected between said header pipes. 